Pollination context and abiotic stress reshape variation in floral longevity and its exposure to selection

Floral longevity is thought to evolve by natural selection imposed by
pollinators and resource constraints acting on heritable phenotypic
variation. In species with pollination-induced wilting, pollination rates
may also influence expression of variation, raising questions of how and
when floral longevity is shaped by adaptation. We created an experimental
range of pollen deposition rates in a wild population of Sabatia angularis
(Gentianaceae) against the backdrop of natural abiotic variation. We
investigated how pollination environment affected expression of longevity,
distribution of variation, phenotypic correlations, and predispersal seed
predation risk. We evaluated whether any effects of abiotic factors are
modified by pollination environment. Mean and variance in floral longevity
declined with increasing pollen deposition rates, and phenotypic
distributions became increasingly compressed. Nevertheless, we detected a
flower lifespan-number trade-off and positive flower lifespan-size
relationship, independent of treatment. Vapor pressure deficit (VPD) and
intraseasonal changes constrained longevity. Suppression associated with
VPD was greatest under low pollen deposition rates, where selection is
expected to favor longer-lived flowers. Floral longevity had weak and
inconsistent effects on predispersal seed predation risk. Our results
demonstrate that phenotypic variation in floral longevity is conditionally
expressed across ecological contexts, altering when variation is exposed
to selection and subsequent evolutionary potential.